Metallurgist

Vol. 39. Nos. 11 - 12, 1995

TECHNICAL-CONTROL SYSTEMS FOR SLAB-CASTING MACHINES A. S. R a i k o v I a n d A. N. S o r o k i n I

Translated from Metallurg, Vol. 39, No. 11, pp. 37 - 38, November, 1995.

In 1990 the Tekhnoap Joint-Stock Company began the development of nonstandard systems for automation of slabcasting machines (SCM) at the request of and in cooperation with the Severstal' JSC. The UZTM JSC, Ekaterinburg, is a partner of the Tekhnoap JSC in the field of continuous casting of steel. The term "nonstandard" refers only to the equipment of Russian SCMs because these systems are ordinary components of modern SCMs in other countries. At present, the following nonstandard process control systems (PCS) are being developed, tested, and furnished by the Severstal' JSC: "Podvisanie," "Zatravka,.... Razlivka,.... Uroven', .... Kalibrator," and "Teplos'em." The "'Podvisanie" system monitors the condition of ingot shells at the output of a crystallizer. This system consists of matrices of special reusable thermal transducers based on constantan -copper thermocouples located on the sides of the crystallizer (eight thermocouples are located on the wide sides and four thermocouples on the narrow sides) inside the pins attaching the plates to the body. Information about the dynamics of the temperature field of the crystallizer is processed according to a special algorithm that evaluates the possibility of the appearance of hangings, including dangerous breaks of the shell, that result in opening of the shell at the output of the crystallizer. This information also makes it possible to estimate the adjustment of the crystallizer and the serviceability of the system of primary cooling. The PCS warns an operator about a possible opening of a shell and the need to decrease the teeming rate. The "Zatravka" system allows monitoring of the parameters of the roller guide and the secondary cooling zone and measurement of the evenness of the main guide axis, the mean roll gap and the wobbling of the rolls, the misalignment of gaps, the velocities of the slips of the rolls, the overheating of the rolls, the thickness of scale on the rolls, and the relative specific heat removal from the surface of the slab by the airwater mixture provided by each of the atomizers. This PCS is designed as a measuring dummy bar with electromagnetic indicators of movements and distances, anemometric indicators of heat removal, and thermocouples. Some 1 0 - 15 min after the drawing the operator receives a report on the condition of the measuring dummy bar. The errors of size measurements

are + 0.1 mm, and thermal parameters are measured with an error o f + 5%. The "Razlivka" system allows monitoring of the parameters of mechanical interaction between the slab and the crystallizer and independent control of the oscillation mechanism. By analyzing the signals of the gauges of acceleration located on the frame of the oscillation mechanism, velocities, and locations in a real time scale, the relative parameters are calculated by special algorithms. The data characterize the quality and quantity of the slag-forming mixture (grease) between the slab and the crystallizer, the force of the slab drawing, the early stages of hanging, and the adjustment of the oscillation mechanism and the crystallizer. This PCS warns the operator when specified threshold values of the parameters are exceeded, thus preventing openings and predicting the slab quality. The "Uroven' '" system is an automated system for stabilizing the metal level in the crystallizer. A distinguishing feature of this system is the use of an inexpensive and easily replaceable inductive indicator of the metal level, which is installed on the edge of the crystallizer, and the use of a safe, accessible, and easily removable electrical-mechanical driver of the ladle stopper based on a commercial low-power dc motor. The operating algorithm of the computerized PCS is designed on an adaptive principle, and therefore, no preliminary adjustment of the system is needed. The "Uroven'" system completely counters the following disturbances appearing during casting: changes in the slab velocity and in the cross sectional area of the tap hole of the stopper due to the sticking of the metal and the aluminum compounds on the stopper surfaces. The error of stabilization of the metal level is no more than + 2 mm in the range of 20 - 150 mm from the upper edge of the copper plates. The maximum force on the rod is 4 kN at a velocity of rod movement of 20 - 30 mm/sec. The "Kalibrator" system is intended for calibration of metal level indicators operating on any principle. The data are presented as absolute values of th distance from a specified base. An automated mode of operation makes it possible to determine the metal level and thus approach the problem of the automated triggering of the SCM. This system may be used in combination with the "Uroven' " system or any other system for stabilization. The "Kalibrator" is designed on the

I Tekhnoap Joint-Stock Company, Moscow, Russia.

208 0026-0894/95/I 112-00208512.50 • 1996 Plenum Publishing Corporation

Technical-Control

Systems for Slab-Casting Machines

basis of an electromechanical monitoring system and expendable contact indicators of the metal level. The calibration range is 0 - 150 mm, and the error is no more than + 1 ram. The "Teplos'em" system controls heat removal in the crystallizer and (for the appropriate assembly) heat removal in the system for cooling the middle supports of the roller guide of the secondary-cooling zone. Operation of this PCS is based on determination of the actual heat removal using the characteristics of consumption and temperature difference. The use of this PCS in the crystallizer makes it possible to predict the slab quality and the possibility of edge cracking. Failure of the support bearings induced by overheating may be predicted, when this PCS is installed in the secondary-cooling zone. This system is built using eddy and / or thermal anemometric airflow meters and temperature gauges (of the platinum or copper group). The general functioning features of the PCSs described above are as follows:

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- accumulation of information and the possibility of displaying this information; - data processing by the desired algorithms and representation of the results; - working out recommendations (prompts) to an operator and / or the automated control of the process; - warning about irregular situations, including pre-emergency ones, recording of the operator's activity, automated data recording and self-control; - reception from and translation of information to a computer network of a higher level. The set of the equipment usually includes the transducers, amplifying and conversion units, cross units, controllers, modems, expanders of the COM ports, IBM commercial personal computers equipped with network adapters, cable lines and / or radio channels, fasteners, spares, supply kit, and software. The electronic units can be ventilated and heated. The equipment is of high strength and dust- and waterproof.